The
Lyre of Ur was one of two bull's-headed harp instruments
that British archaeologist Sir Leonard Woolley recovered
from a mass grave during his highly publicised excavations
of Ur's Royal Cemetery in the 1920s and 30s in Iraq. Recreated
unplayable models of the Lyre are held in Pennsylvania,
London and, until recently before it was vandalised, the
Baghdad Museum. It is believed that the original Lyre
is approximately 4750 years old. An attempt to recreate
an authentic playable version is being spearheaded by
Mr A Lowings of Stamford. The instrument is to be ornamented
by a golden-sheeted bull's head and geometrically inlaid
lapis lazuli as well as engraved gulf pearl shell plaques
depicting Sumerian images, which are to be placed on the
front of the lyre. Authentic cedar wood from Baghdad was
used to create the main framework of the lyre. Due to
the intricate designs required for the shell plaques an
investigation to laser engrave them was undertaken. The
main objective when laser engraving the pearl shells (which
are chiefly calcium carbonate) was to achieve sufficient
depth without compromising image quality so that the plaques
could be backfilled with bitumen in order to replicate
the originals. Moreover, it was imperative to recreate
the images without damage to the surrounding pearl either
by scorching or re-depositing removed material. Experiments
were carried out to engrave the shells utilising a Synrad
CO2 laser which has galvanometer controlled mirrors to
direct the beam which enables it to be scanned in an XY
direction across the surface of the target material. An
image software package was used in conjunction with the
laser so that the images could be manipulated in terms
of size and positioning. It was necessary to remove excess
material produced between successive laser passes using
a soft brush to allow full penetration of the laser beam
to the newly created lower surface level. Successful engraving
was achieved using multiple laser passes and an identified
optimum-processing window.